1. Field of the Invention
The present invention relates to a light source for generating an optical signal, and more particularly to a light source including an optical detector for detecting intensity of an optical signal.
2. Description of the Related Art
Optical communication systems and various digital media require low-priced, miniaturized and effective light sources. Semiconductor-type light sources, such as a semiconductor laser, are widely used as general light sources. For example, distributed feedback lasers or Fabry-Perot lasers may be used as the above-mentioned semiconductor laser.
Such semiconductor lasers may be embodied as an integrated type, provided with an electric-absorptive modulator for modulating generated light, on a single substrate. Such integrated type devices are advantageous because it is possible to minimize the semiconductor laser product or system.
However, such semiconductor lasers have a shortcoming because the intensity of light output from the semiconductor laser varies according to the variation in external temperature, driving current and operation time. Accordingly, such conventional light sources must further include a means for continuously monitoring and maintaining the intensity of the output optical signal.
FIG. 1 is a schematic view of a conventional semiconductor optical element. The conventional semiconductor optical element includes a semiconductor light source 120 and an optical detector 110 positioned in the rear of the semiconductor light source 120.
The semiconductor light source 120 employs a reflection-type semiconductor optical amplifier, a distributed feedback laser, and a Fabry-Perot laser, which outputs first and second light signals respectively through both terminals thereof. A non-reflective layer is formed on one terminal of the semiconductor light source 120 for outputting the first light therethrough, and a high-reflective layer is formed on the other terminal of the semiconductor light source 120 for outputting the second light therethrough. The second light signal is a part of the first light signal passing through the high-refection layer.
The optical detector 110 detects the second light signal output from the semiconductor light source 120. In this way, the intensity of the first light signal output from the semiconductor light source 120 is monitored.
FIG. 2 is a schematic view of a conventional semiconductor optical element including a beam splitter. The conventional semiconductor optical element shown in FIG. 3 includes a semiconductor light source 210, an optical detector 220, and a beam splitter 230 for a splitting light signal output from the semiconductor light source 210. A portion of the split light signal is then input to the optical detector 220.
The beam splitter 230 serves to split light signal output from the semiconductor light source 210 and then inputs part of the split light signal to the optical detector 220. The optical detector 220 detects the part of the light output from the beam splitter 230 and monitors the intensity of light output from the semiconductor light source 210.
The intensity of the light output from the rear terminal of the light source is linearly converted from the intensity of the light output from the front terminal of the light source in the above conventional semiconductor optical elements. However, it is difficult to accurately calculate the intensity of the light output from the front terminal of the light source.
In addition, the conventional semiconductor optical element shown in FIG. 1 is restrictedly used only in cases where the ratio of output of the light from the front terminal to the rear terminal of the Fabry-Perot laser, or etc. including a reflection mirror or reflective layer positioned in the rear of the light source is uniform.
Moreover, in the conventional semiconductor optical element shown in FIG. 2 , the beam splitter splits light output from the light source, which complicates the structure of the semiconductor optical element and also increases the loss in the intensity of the light.